How will the new dengue vaccine be introduced to have the most impact?

Getting the most out of the new dengue vaccine investing in logistics, surveillance, and diagnostics

The world’s first dengue vaccine, introduced by Sanofi Pasteur, has been given the green light in Mexico, the Philippines, and Brazil. More countries in Latin America and South-east Asia are preparing to follow. But how can we be sure the vaccine gets to those who need it, and what needs to be done to measure its true impact?

Prof. Usa Thisyakorn

Professor Usa Thisyakorn, a consultant at the Faculty of Tropical Medicine at the Mahidol University in Thailand, says that doctors in dengue-affected areas have been crying out for a dengue vaccine for a long time and are ready to embrace it.

“For health professionals and for the general population, dengue is a high priority and the vaccine is long-awaiting,” she said.

However, while many ASEAN countries have well-developed childhood immunization programs, reaching adolescents and adults is a new challenge.

“On top of that, there are always practical challenges like safeguarding the cold chain – to keep vaccines at the appropriate temperature – when transporting them.”

In the WHO’s Global Strategy for Dengue Prevention and Control 2012-2020, the Organisation says vaccines can change how we look at dengue prevention. But the report makes the point that vaccines are only of value when they reach those who need them: “Even a perfect vaccine is only as good as our ability to deliver it.”

The strategy sets out five key elements to breaking dengue:

Diagnosis and case management

Integrated surveillance and outbreak preparedness

Sustainable vector control

Vaccine implementation

Basic, operational and implementation research

Surveillance: a mixed picture

The arrival of dengue vaccines does not mean neglecting other key elements of dengue control such as surveillance, diagnosis, and management as well as vector control. On the contrary – the vaccine is most powerful when used as part of a holistic approach to defeating the disease.

“The 10 ASEAN countries have been working together for several years, following WHO technical advice, to improve surveillance,” explains Professor Thisyakorn. “Surveillance infrastructure is not the same across the region – some countries have very strong systems, others are still developing.”

One of the big challenges is to use common case definition and surveillance criteria. This will help to show where the vaccine is most effective, potentially highlighting any differences between regions or age groups. Standard and consistent surveillance, as well as diagnostics and management, will give an accurate picture of the impact of the vaccine.

However, while some countries have access to state-of-the-art laboratory testing, others rely on clinical symptoms to diagnose the disease.

“There is great diversity from country to country. Some areas have all the modern diagnostic tests available while others rely on clinical diagnosis which is not always as accurate,” says Professor Thisyakorn.

In Bangkok, for example, surveillance systems are very advanced and public health experts use sophisticated mathematical modeling to track epidemics and predict the likely impact of health interventions. But in some countries, the lab infrastructure is significantly weaker.

Changing behaviours

One factor not causing major concern in the region is public attitudes to vaccination. While some developed nations have seen immunization rates dip due to vaccine hesitancy – perhaps due to complacency about infectious diseases – Southeast Asian countries have not had this problem.

“Everyone has been longing for an efficacious and safe vaccine against dengue,” says Professor Thisyakorn. “Confidence in existing vaccination programs is high so we don’t anticipate a problem with public acceptance.”

However, with new tools now at the disposal of health officials, the public will need to be educated about who should have the vaccine and how they can access it. Changing behavior is tricky – as vector control campaigns have shown.

“People have been educated about vector control but we are still seeing higher numbers of dengue cases every year. We have to continue to educate but also try something new, like vaccination,” Professor Thisyakorn says. “We must also communicate with other stakeholders and try to connect vaccination with existing dengue initiatives.”

While much work lies ahead to maximize the impact of dengue vaccines, public health experts are excited about writing a new chapter in the dengue story.